A Research-Based Approach to the Learning and Teaching of Physics David E. Meltzer Department of...

A Research-Based Approach to the Learning and Teaching of Physics

David E. Meltzer

Department of Physics

University of Washington

Collaborators– Mani Manivannan (Missouri State University)

– Tom Greenbowe (Iowa State University, Chemistry)

– John Thompson (University of Maine, Physics)

Students– Tina Fanetti (ISU, M.S. 2001)

– Jack Dostal (ISU, M.S. 2005)

– Ngoc-Loan Nguyen (ISU, M.S. 2003)

– Warren Christensen (ISU Ph.D. student)

Funding– NSF Division of Undergraduate Education

– NSF Division of Research, Evaluation, and Communication

– NSF Division of Physics

Outline1. Physics Education as a Research Problem

Methods of physics education research

2. Research-Based Instructional Methods

Principles and practices

3. Research-Based Curriculum Development

A “model” problem: law of gravitation

4. Recent Work: Student Learning of Thermal Physics

Research and curriculum development

Physics Education As a Research Problem

Within the past 25 years, physicists have begun to treat the teaching and learning of physics as a research problem

• Systematic observation and data collection; reproducible experiments

• Identification and control of variables

• In-depth probing and analysis of students’ thinking

Physics Education Research (“PER”)

Goals of PER

• Improve effectiveness and efficiency of physics instruction– guide students to learn concepts in greater depth

• Develop instructional methods and materials that address obstacles which impede learning

• Critically assess and refine instructional innovations

Methods of PER

• Develop and test diagnostic instruments that assess student understanding

• Probe students’ thinking through analysis of written and verbal explanations of their reasoning, supplemented by multiple-choice diagnostics

• Assess learning through measures derived from pre- and post-instruction testing

What PER Can NOT Do

• Determine “philosophical” approach toward undergraduate education

– e.g., focus on majority of students, or on subgroup?

• Specify the goals of instruction in particular learning environments– proper balance among “concepts,” problem-solving, etc.

Role of Researchers in Physics Education

• Carry out in-depth investigations of student thinking in physics– provide basis for “pedagogical content knowledge”

• Develop and assess courses and curricula:– for introductory and advanced undergraduate

courses– for physics teacher preparation

Progress in Teacher Preparation

• Advances in research-based physics education have motivated changes in physics teacher preparation programs.

• There is an increasing focus on research-based “active-engagement” instructional methods and curricula.

• Examples: Physics by Inquiry curriculum (Univ.

Washington); Modeling Workshops (Arizona State U.)

Example: Course for Physics-Teacher Preparation

• Course taught by D.E.M., for students planning to teach high-school physics (at Iowa State U.)

– includes pre-service and in-service teachers, students with and without B.A., diverse majors

• Reading and discussion of physics education research literature

• In-class instruction using research-based curricular materials (guided by course instructor)

• Students prepare and deliver own lesson– modeled on research-based instructional materials

Example: Inquiry-Based Physics Course for Non-technical Students

• Developed and taught by D.E.M., targeted especially at education majors (i.e., “teachers in training”).

• Taught at Southeastern Louisiana University for 8 consecutive semesters; average enrollment: 14

• One-semester course, met 5 hours per week in lab– focused on hands-on activities; no formal lecture.

• Inquiry-based learning: targeted concepts not told to students before they work to “discover” them through group activities.

Research and Scholarship in Physics-Teacher Preparation

• Forthcoming book of collected papers

• Jointly published by American Physical Society and American Association of Physics Teachers

• Editor: D.E.M.

• Associate Editor: Peter Shaffer (U. Washington)

Research Basis for Improved Learning

• “Pedagogical Content Knowledge” (Shulman, 1986): Knowledge needed to teach a specific topic effectively, beyond general knowledge of content and teaching methods

“the ways of representing and formulating a subject that make it comprehensible to othersan understanding of what makes the learning of specific topics easy or difficultknowledge of the [teaching] strategies most likely to be fruitful”

Research on Student Learning: Some Key Results

• Students’ subject-specific conceptual difficulties play a significant role in impeding learning;

• Inadequate organization of students’ knowledge is a key obstacle.– need to improve linking and accessibility of ideas

• Students’ beliefs and practices regarding learning of science should be addressed.– need to stress reasoning instead of memorization

A Model for Students’ Knowledge Structure

[E. F. Redish, AJP (1994), Teaching Physics (2003)]

Archery Target: three concentric rings

• Central black bull’s-eye: what students know well

– tightly linked network of well-understood concepts• Middle “gray” ring: students’ partial and imperfect

knowledge [Vygotsky: “Zone of Proximal Development”]

– knowledge in development: some concepts and links strong, others weak

• Outer “white” region: what students don’t know at all

– disconnected fragments of poorly understood concepts, terms and equations




• Central black bull’s-eye: what students know well– tightly linked network of well-understood concepts

• Middle “gray” ring: students’ partial and imperfect knowledge [Vygotsky: “Zone of Proximal Development”]


• Outer “white” region: what students don’t know at all

– disconnected fragments of poorly understood concepts, terms and equations




• Central black bull’s-eye: what students know well– tightly linked network of well-understood concepts

• Middle “gray” ring: students’ partial and imperfect knowledge [Vygotsky: “Zone of Proximal Development”]


• Outer “white” region: what students don’t know at all– disconnected fragments of poorly understood ideas

Schematic Representation of Knowledge Structure

well-defined, correct concept

explicit but incorrect concept

ill-defined idea

consistent, reliable link

inconsistent, unpredictable link

“Bulls-eye” region:Well-structured knowledge

[F. Reif, Am. J. Phys. (1995)]

“Gray” region:incomplete, loosely structured knowledge

“White” region:incoherent ideas

Teaching Effectiveness, Region by Region

• In central black region: difficult to make significant relative gains

• In white region: learning gains minor, infrequent, and poorly retained.

• Teaching most effective when targeted at gray: Analogous to substance near phase transition; a few key concepts and links can catalyze substantial leaps in student understanding.

Research Task: map out gray region

Instructional Task: address difficulties in gray region

Instructional Goal: well-organized set of coherent concepts

Research-Based Instruction

• Recognize and address students’ pre-instruction “knowledge state” and learning tendencies, including:– subject-specific learning difficulties– potentially productive ideas and intuitions– student learning behaviors

• Guide students to address learning difficulties through structured and targeted problem-solving activities.

Some Specific Issues

Many (if not most) students:

• develop weak qualitative understanding of concepts

– don’t use qualitative analysis in problem solving– lacking quantitative problem solution, can’t reason

“physically”

• lack a “functional” understanding of concepts (which would allow problem solving in unfamiliar contexts)

But … some students learn efficiently . . .

• Highly successful physics students are “active learners.”

– they continuously probe their own understanding [pose their own questions; scrutinize implicit assumptions; examine

varied contexts; etc.]

– they are sensitive to areas of confusion, and have the confidence to confront them directly

• Majority of introductory students are unable to do efficient active learning on their own: they don’t know “which questions they need to ask”

– they require considerable assistance from instructors, aided by appropriate curricular materials

Research in physics education suggests that:

• Problem-solving activities with rapid feedback yield improved learning gains

• Eliciting and addressing common conceptual difficulties improves learning and retention

Active-Learning Pedagogy(“Interactive Engagement”)

• problem-solving activities during class time – student group work– frequent question-and-answer exchanges

• “guided-inquiry” methodology: guide students with leading questions, through structured series of research-based problems dress common learning

Goal: Guide students to “figure things out for themselves” as much as possibleuide students to “figure things out for themselves” as much as possible

Key Themes of Research-Based Instruction

• Emphasize qualitative, non-numerical questions to reduce unthoughtful “plug and chug.”

• Make extensive use of multiple representations to deepen understanding.

(Graphs, diagrams, words, simulations, animations, etc.)

• Require students to explain their reasoning (verbally or in writing) to more clearly expose their thought processes.

Active Learning in Large Physics Classes

• De-emphasis of lecturing; Instead, ask students to respond to questions targeted at known difficulties.

• Use of classroom communication systems to obtain instantaneous feedback from entire class.

• Incorporate cooperative group work using both multiple-choice and free-response items

Goal: Transform large-class learning environment into “office” learning environment (i.e., instructor + one or two students)

Active Learning in Large Physics Classes

• De-emphasis of lecturing; Instead, ask students to respond to questions targeted at known difficulties.

• Use of classroom communication systems to obtain instantaneous feedback from entire class.

• Incorporate cooperative group work using both multiple-choice and free-response items

Analogous to in-class strategies used with Just-In-Time Teaching (Novak, Gavrin, Christian, and Patterson, 1999)

“Fully Interactive” Physics LectureDEM and K. Manivannan, Am. J. Phys. 70, 639 (2002)

• Use structured sequences of multiple-choice questions, focused on specific concept: small conceptual “step size”

• Use student response system to obtain instantaneous responses from all students simultaneously (e.g., “flash cards”)

[a variant of Mazur’s “Peer Instruction”]

Interactive Question Sequence

• Set of closely related questions addressing diverse aspects of single concept

• Progression from easy to hard questions

• Use multiple representations (diagrams, words, equations, graphs, etc.)

• Emphasis on qualitative, not quantitative questions, to reduce “equation-matching” behavior and promote deeper thinking

Results of Assessment

• Learning gains on qualitative problems are well above national norms for students in traditional courses.

• Performance on quantitative problems is comparable to (or slightly better than) that of students in traditional courses.

Assessment DataScores on Conceptual Survey of Electricity and Magnetism, 14-

item electricity subset

Sample N

National sample (algebra-based)

402

National sample (calculus-based)

1496

D. Maloney, T. O’Kuma, C. Hieggelke, and A. Van Heuvelen, PERS of Am. J. Phys. 69, S12 (2001).



Sample N


402


1496



Sample N Mean pre-test score


402 27%


1496



Sample N Mean pre-test score


402 27%


1496 37%



Sample N Mean pre-test score Mean post-test score


402 27% 43%


1496 37% 51%





402 27% 43%


1496 37% 51%

ISU 1998 70 30%

ISU 1999 87 26%

ISU 2000 66 29%





402 27% 43%


1496 37% 51%

ISU 1998 70 30% 75%

ISU 1999 87 26% 79%

ISU 2000 66 29% 79%

Quantitative Problem Solving: Are skills being sacrificed?

N Mean Score

Physics 221: F97 & F98

Six final exam questions320 56%

Physics 112: F98



Subset of three questions372 59%

Physics 112: F98, F99, F00


Quantitative Problem Solving: Are skills being sacrificed?

ISU Physics 112 compared to ISU Physics 221 (calculus-based), numerical final exam questions on electricity

N Mean Score



Physics 112: F98




Physics 112: F98, F99, F00


Research-Based Curriculum Development Example: Thermodynamics Project

• Investigate student learning in actual classes; probe learning difficulties

• Develop new materials based on research

• Test and modify materials

• Iterate as needed

Addressing Learning Difficulties: A Model Problem

Student Concepts of Gravitation[Jack Dostal and DEM]

• 10-item free-response diagnostic administered to over 2000 ISU students during 1999-2000.– Newton’s third law in context of gravity; direction and superposition of

gravitational forces; inverse-square law.

• Worksheets developed to address learning difficulties; tested in Physics 111 and 221, Fall 1999



• 10-item free-response diagnostic administered to over 2000 ISU students during 1999-2000.– Newton’s third law in context of gravity, inverse-square law, etc.

• Worksheets developed to address learning difficulties; tested in Physics 111 and 221, Fall 1999



• 10-item free-response diagnostic administered to over 2000 ISU students during 1999-2000.– Newton’s third law in context of gravity, inverse-square law, etc.

• Worksheets developed to address learning difficulties; tested in calculus-based physics course Fall 1999

Example: Newton’s Third Law in the Context of Gravity

Is the magnitude of the force exerted by the asteroid on the Earth larger than, smaller than, or the same as the magnitude of the force exerted by the

Earth on the asteroid? Explain the reasoning for your choice.

[Presented during first week of class to all students taking calculus-based introductory physics (PHYS 221-222) at ISU during Fall 1999.]

First-semester Physics (N = 546): 15% correct responses

Second-semester Physics (N = 414): 38% correct responses

Most students claim that Earth exerts greater force because it is larger

Earthasteroid

Example: Newton’s Third Law in the Context of Gravity

Is the magnitude of the force exerted by the asteroid on the Earth larger than, smaller than, or the same as the magnitude of the force exerted by the

Earth on the asteroid? Explain the reasoning for your choice.

[Presented during first week of class to all students taking calculus-based introductory physics at ISU during Fall 1999.]

First-semester Physics (N = 546): 15% correct responses

Second-semester Physics (N = 414): 38% correct responses

Most students claim that Earth exerts greater force because it is larger

Earthasteroid

Implementation of Instructional Model“Elicit, Confront, Resolve” (U. Washington)

• Pose questions to students in which they tend to encounter common conceptual difficulties

• Allow students to commit themselves to a response that reflects conceptual difficulty

• Guide students along reasoning track that bears on same concept

• Direct students to compare responses and resolve any discrepancies

Implementation of Instructional Model“Elicit, Confront, Resolve” (U. Washington)

One of the central tasks in curriculum reform is development of “Guided Inquiry” worksheets

• Worksheets consist of sequences of closely linked problems and questions– focus on conceptual difficulties identified through research– emphasis on qualitative reasoning

• Worksheets designed for use by students working together in small groups (3-4 students each)

• Instructors provide guidance through “Socratic” questioning

Example: Gravitation Worksheet (Jack Dostal and DEM)

• Design based on research, as well as instructional experience

• Targeted at difficulties with Newton’s third law, and with use of proportional reasoning in inverse-square force law

Name_______________________Gravitation WorksheetPhysics 221

a) In the picture below, a person is standing on the surface of the Earth.Draw an arrow (a vector) to represent the force exerted by the Earthon the person.

b) In the picture below, both the Earth and the Moon are shown. Drawan arrow to represent the force exerted by the Earth on the Moon.Label this arrow (b).

c) Now, in the same picture (above), draw an arrow which represents theforce exerted by the Moon on the Earth. Label this arrow (c).Remember to draw the arrow with the correct length and direction ascompared to the arrow you drew in (b).

d) Are arrows (b) and (c) the same size? Explain why or why not.

Earth

Earth

Moon






Earth

Earth

Moonb






Earth

Earth

Moon

common student response

bc

e) Consider the magnitude of the gravitational force in (b). Write down an algebraic expression for the strength of the force. (Refer to Newton’s Universal Law of Gravitation at the top of the previous page.) Use Me for the mass of the Earth and Mm

for the mass of the Moon. f) Consider the magnitude of the gravitational force in (c). Write down an algebraic expression for the strength of the force. (Again, refer to Newton’s Universal Law of Gravitation at the top of the previous page.) Use Me for the mass of the Earth and Mm

for the mass of the Moon. g) Look at your answers for (e) and (f). Are they the same? h) Check your answers to (b) and (c) to see if they are consistent with (e) and (f). If necessary, make changes to the arrows in (b) and (c).




2r

MMGF me

b =




2r

MMGF me

b =

2r

MMGF me

c =






Earth

Earth

Moon

common student response

bc

Name_______________________ Gravitation Worksheet Physics 221

a) In the picture below, a person is standing on the surface of the Earth. Draw an arrow (a vector) to represent the force exerted by the Earth on the person.

b) In the picture below, both the Earth and the Moon are shown. Draw

an arrow to represent the force exerted by the Earth on the Moon. Label this arrow (b).

c) Now, in the same picture (above), draw an arrow which represents the

force exerted by the Moon on the Earth. Label this arrow (c). Remember to draw the arrow with the correct length and direction as compared to the arrow you drew in (b).


Earth

Earth

Moon

corrected student response

bc

Final Exam Question #1

A. The gravitational force exerted by the chunk of ice on Saturn is greater than the gravitational force exerted by Saturn on the chunk of ice.

B. The gravitational force exerted by the chunk of ice on Saturn is the same magnitude as the gravitational force exerted by Saturn on the chunk of ice.

C. The gravitational force exerted by the chunk of ice on Saturn is nonzero, and less than the gravitational force exerted by Saturn on the chunk of ice.

D. The gravitational force exerted by the chunk of ice on Saturn is zero.

E. Not enough information is given to answer this question.

The rings of the planet Saturn are composed of millions of chunks of icy debris. Consider a chunk of ice in one of Saturn's rings. Which of the following statements is true?

Final Exam Question #1 (Fall 1999, Calculus-Based Course)

0

20

40

60

80

100

Per

cent

Cor

rect

Res

pons

e

Non-Worksheet (N = 384)

Worksheet (N = 116)

Error Bars: 95% confidence interval


0

20

40

60

80

100

Per

cent

Cor

rect

Res

pons

e


Worksheet (N = 116)


After correction for difference between recitation attendees and non-attendees

Final Exam Question #2

Final Exam Question #2Two lead spheres of mass M are separated by a distance r.

They are isolated in space with no other masses nearby. The magnitude of the gravitational force experienced by each mass is F. Now one of the masses is doubled, and they are pushed farther apart to a separation of 2r. Then, the magnitudes of the gravitational forces experienced by the masses are:

A. equal, and are equal to F.

B. equal, and are larger than F.

C. equal, and are smaller than F.

D. not equal, but one of them is larger than F.

E. not equal, but neither of them is larger than F.


0

20

40

60

80

100

Per

cen

t C

orr

ect

Res

po

nse


Worksheet (N = 116)


After correction for difference between recitation attendees and non-attendees

Research on the Teaching and Learning of Thermal Physics

• Investigate student learning of classical and statistical thermodynamics

• Probe evolution of students’ thinking from introductory through advanced-level course

• Develop research-based curricular materials

In collaboration with John Thompson, University of Maine

Studies of university students in general physics courses have revealed substantial learning difficulties with fundamental concepts, including heat, work, and the first and second laws of thermodynamics:

USAM. E. Loverude, C. H. Kautz, and P. R. L. Heron (2002);

D. E. Meltzer (2004);

M. Cochran and P. R. L. Heron (2006).

GermanyR. Berger and H. Wiesner (1997)

FranceS. Rozier and L. Viennot (1991)

UKJ. W. Warren (1972)

Student Learning of Thermodynamics

Primary Findings, Introductory Course

Even after instruction, many students (40-80%):

• believe that heat and/or work are state functions independent of process

• believe that net work done and net heat absorbed by a system undergoing a cyclic process must be zero

• are unable to apply the First Law of Thermodynamics in problem solving

Upper-level Thermal Physics Course

• Topics: classical macroscopic thermodynamics; statistical thermodynamics

• Students enrolled [Ninitial = 14 (2003) and 19 (2004)]

90% were physics majors or physics/engineering double majors

90% were juniors or above

– all had studied thermodynamics (some at advanced level)

Performance Comparison: Upper-level vs. Introductory Students

• Diagnostic questions given to students in introductory calculus-based course after instruction was complete:

– 1999-2001: 653 students responded to written questions

– 2002: 32 self-selected, high-performing students participated in one-on-one interviews

• Written pre-test questions given to Thermal Physics students on first day of class

0

5

10

15

20

25

30

Total Grade Points

Per

cen

tag

e o

f Sam

ple

Full Class, N = 424, median grade = 261

Interview Sample, N = 32, median grade = 305

Interview Sample:34% above 91st percentile; 50% above 81st percentile

Grade Distributions: Interview Sample vs. Full Class

This P-V diagram represents a system consisting of a fixed amount of ideal gas that undergoes two different processes in going from state A to state B:


[In these questions, W represents the work done by the system during a process; Q represents the heat absorbed by the system during a process.] 1. Is W for Process #1 greater than, less than, or equal to that for Process #2? Explain. 2. Is Q for Process #1 greater than, less than, or equal to that for Process #2?



B

A

V

VdVPW



B

A

V

VdVPW W1 > W2

Responses to Diagnostic Question #1 (Work question)

1999-2001Introductory

Physics (Post-test)

Written Sample(N=653)

2002Introductory

Physics(Post-test)

Interview Sample (N=32)

2004Thermal Physics(Pretest)

(N=19)

W1 > W2

W1 = W2

W1 < W2



Physics (Post-test)


2002Introductory

Physics(Post-test)



(N=21)

W1 = W2 30% 22% 24%



Physics (Post-test)


2002Introductory

Physics(Post-test)



(N=14)

W1 = W2 30% 22% 20%



Physics (Post-test)


2002Introductory

Physics(Post-test)



(N=19)

W1 = W2 30% 22% 20%



Physics (Post-test)


2002Introductory

Physics(Post-test)



(N=19)

W1 = W2 30% 22% 20%

About one-quarter of all students believe work done is equal in both processes

• “Equal, path independent.”

• “Equal, the work is the same regardless of path taken.”

Some students come to associate work with phrases only used in connection with state functions.

Explanations Given by Thermal Physics Students to Justify W1 = W2

Explanations similar to those offered by introductory students

• “Equal, path independent.”

• “Equal, the work is the same regardless of path taken.”

Some students come to associate work with phrases only used in connection with state functions.

Explanations Given by Thermal Physics Students to Justify W1 = W2

Confusion with mechanical work done by conservative forces?



Change in internal energy is the same for Process #1 and Process #2.



Change in internal energy is the same for Process #1 and Process #2.

The system does more work in Process #1, so it must absorb more heat to reach same final value of internal energy: Q1 > Q2

Responses to Diagnostic Question #2 (Heat question)


Physics (Post-test)


2002Introductory

Physics(Post-test)



(N=19)

Q1 > Q2

Q1 = Q2

Q1 < Q2


Q1 = Q2


1999-2001Introductory Physics

(Post-test)


Q1 = Q2 38%



(Post-test)


2002Introductory Physics

(Post-test)


Q1 = Q2 38% 47%



(Post-test)



(Post-test)


2003-4Thermal Physics

(Pretest)

(N=33)

Q1 = Q2 38% 47% 30%

Explanations Given by Thermal Physics Students to Justify Q1 = Q2

• “Equal. They both start at the same place and end at the same place.”

• “The heat transfer is the same because they are starting and ending on the same isotherm.”

Many Thermal Physics students stated or implied that heat transfer is independent of process, similar to claims made by introductory students.



Physics (Post-test)


2002Introductory

Physics(Post-test)



(N=19)

Q1 > Q2

Q1 = Q2

Q1 < Q2



(Post-test)



(Post-test)


2004Thermal Physics

(Pretest)

(N=21)

Q1 > Q2 45% 34% 33%

[Correct answer] 11% 19% 33%



(Post-test)



(Post-test)


2004Thermal Physics

(Pretest)

(N=21)

Q1 > Q2 45% 34% 33%

Correct or partially correct explanation

11% 19% 33%



(Post-test)



(Post-test)


2003Thermal Physics

(Pretest)

(N=14)

Q1 > Q2 45% 34% 35%


11% 19% 33%



(Post-test)



(Post-test)


2003Thermal Physics

(Pretest)

(N=14)

Q1 > Q2 45% 34% 35%


11% 19% 30%



(Post-test)



(Post-test)


2004Thermal Physics

(Pretest)

(N=19)

Q1 > Q2 45% 34% 30%


11% 19% 30%



(Post-test)



(Post-test)


2004Thermal Physics

(Pretest)

(N=19)

Q1 > Q2 45% 34% 30%


11% 19% 30%

Performance of upper-level students better than that of most introductory students, but still weak

Primary Findings, Introductory Course

Even after instruction, many students (40-80%):

• believe that heat and/or work are state functions independent of process

• believe that net work done and net heat absorbed by a system undergoing a cyclic process must be zero

• are unable to apply the First Law of Thermodynamics in problem solving

Cyclic Process Questions

A fixed quantity of ideal gas is contained within a metal cylinder that is sealed with a movable, frictionless, insulating piston.

The cylinder is surrounded by a large container of water with high walls as shown. We are going to describe two separate processes, Process #1 and Process #2.

Time A

Entire system at room temperature.waterideal gas

movable piston

At initial time A, the gas, cylinder, and water have all been sitting in a room for a long period of time, and all of them are at room temperature

[This diagram was not shown to students]


initial state

Beginning at time A, the water container is gradually heated, and the piston very slowly moves upward.

At time B the heating of the water stops, and the piston stops moving

containerslead weight

Now, empty containers are placed on top of the piston as shown.


Small lead weights are gradually placed in the containers, one by one, and the piston is observed to move down slowly.

While this happens the temperature of the water is nearly unchanged, and the gas temperature remains practically constant.

At time C we stop adding lead weights to the container and the piston stops moving. The piston is now at exactly the same position it was at time A .


TBC = 0

Now, the piston is locked into place so it cannot move, and the weights are removed from the piston.

The system is left to sit in the room for many hours.

Eventually the entire system cools back down to the same room temperature it had at time A.

After cooling is complete, it is time D.

Question #6: Consider the entire process from time A to time D.

(i) Is the net work done by the gas on the environment during that process (a) greater than zero, (b) equal to zero, or (c) less than zero?

(ii) Is the total heat transfer to the gas during that process (a) greater than zero, (b) equal to zero, or (c) less than zero?


|WBC| > |WAB|


|WBC| > |WAB|

WBC < 0


|WBC| > |WAB|

WBC < 0 Wnet < 0

Results on Question #6 (i)

(c) Wnet < 0: [correct]

Interview sample [post-test]: 19%

2004 Thermal Physics [pre-test]: 10%

(b) Wnet = 0:



Typical explanation offered for Wnet = 0:

“The physics definition of work is like force times distance. And basically if you use the same force and you just travel around in a circle and come back to your original spot, technically you did zero work.”


U = Q – W


U = Q – W

U = 0 Qnet = Wnet


U = Q – W

U = 0 Qnet = Wnet

Wnet < 0 Qnet < 0

Results on Question #6 (ii)

(c) Qnet < 0: [correct]



(b) Qnet = 0:



Explanation offered for Qnet = 0

.


“The heat transferred to the gas . . . is equal to zero . . . . The gas was heated up, but it still returned to its equilibrium temperature. So whatever energy was added to it was distributed back to the room.”



Common response offered by both introductory and upper-level students



Reflects confusion of heat with temperature

Some Strategies for Instruction

• Loverude et al.: Solidify students’ concept of work in mechanics context (e.g., positive and negative work);

• Develop and emphasize concept of work as an energy-transfer mechanism in thermodynamics context.

Some Strategies for Instruction

• Guide students to make increased use of PV-diagrams and similar representations.

• Practice converting between a diagrammatic representation and a physical description of a given process, especially in the context of cyclic processes.

Thermodynamics Curricular Materials

• Preliminary versions and initial testing of worksheets for:

– calorimetry– thermochemistry– first-law of thermodynamics– cyclic processes– Carnot cycle– entropy– free energy

Thermodynamics Curricular Materials

• Preliminary versions and initial testing of worksheets for:

– calorimetry– thermochemistry– first-law of thermodynamics– cyclic processes– Carnot cycle– entropy– free energy

Preliminary testing in general physics and in junior-level thermal physics course

For each of the following questions consider a system undergoing a naturally occurring (“spontaneous”) process. The system can exchange energy with its surroundings.

A. During this process, does the entropy of the system [Ssystem] increase, decrease, or remain the same, or is this not determinable with the given information? Explain your answer.

B. During this process, does the entropy of the surroundings [Ssurroundings] increase, decrease, or remain the same, or is this not determinable with the given information? Explain your answer.

C. During this process, does the entropy of the system plus the entropy of the

surroundings [Ssystem + Ssurroundings] increase, decrease, or remain the same, or is this not determinable with the given information? Explain your answer.

Spontaneous Process Question[Introductory-Course Version]

Responses to Spontaneous-Process Questions

0

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80

100

Co

rre

ct

res

po

ns

es

(%

)

S(system) S(surroundings) S(total)

Intro Physics, Pretest

Intro Physics, Posttest

Thermal Physics, Pretest

Thermal Physics, Posttest

Introductory Students

Less than 40% correct on each question

Introductory Physics Students’ Thinking on Spontaneous Processes

• Tendency to assume that “system entropy” must always increase

• Slow to accept the idea that entropy of system plus surroundings increases

Most students give incorrect answers to all three questions

Entropy Tutorial(draft by W. Christensen and DEM, undergoing class testing)

Insulated cube at TH

Insulated cube at TL Conducting Rod

• Consider slow heat transfer process between two thermal reservoirs (insulated metal cubes connected by thin metal pipe)

Does total energy change during process?

Does total entropy change during process?

[No]

[Yes]

• Guide students to find that:

and that definitions of “system” and “surroundings” are arbitrary

0T

QT

QΔS

reservoirhotreservoircoldtotal

Entropy Tutorial(draft by W. Christensen and DEM, undergoing class testing)

Preliminary results are promising…

Entropy gain of low-temperature cube is larger than entropy loss of high-temperature cube, sototal entropy increases

0%

10%

20%

30%

40%

50%

60%

70%

80%

S(total) correct All three questions correct

Pre-instruction (N = 1184)

Post-instruction, no tutorial (N = 255)

Post-instruction, with tutorial (N = 237)

Responses to Spontaneous-Process Questions Introductory Students

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

S(total) correct All three questions correct

Pre-instruction Post-instruction, with tutorial

Responses to Spontaneous-Process Questions Intermediate Students (N = 32, Matched)

Summary

• Research on student learning lays basis for development of improved instructional materials.

• “Interactive-engagement” instruction using research-based curricula can improve student learning.

• Ongoing development and testing of instructional materials lays the basis for new directions in research, holds promise for sustained improvements in learning.

Summary

• Research on student learning lays basis for development of improved instructional materials in science education.


• Ongoing development and testing of instructional materials lays the basis for new directions in research, holds promise for sustained improvements in learning.

Summary

• Research on student learning lays basis for development of improved instructional materials in science education.


• Treating science education as a research problem holds promise of cumulative progress, based on solid foundation of previous results.

A Research-Based Approach to the Learning and Teaching of Physics David E. Meltzer Department of...

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Transcript of A Research-Based Approach to the Learning and Teaching of Physics David E. Meltzer Department of...